Conventionally, styrene-containing resins, such as AS resin, polystyrene, high impact polystyrene, and ABS resin, are known to exhibit superior moldability, mechanical strength, and external appearance.
There are cases where flame-retardant characteristics are required in these styrene resins, depending on the service. These characteristics are particularly useful in the case of household products, electrical appliances, OA equipment, and the like, and for automotive products and building materials.
A commonly known method of imparting flame retardancy to styrene-containing resins consists of blending a flame retarder. In many cases, the type of flame retarder used is a brominated diphenyl oxide compound, a brominated polycarbonate compound, or the like. A superior flame-retardant effect is demonstrated when these flame retarders are blended with antimony trioxide.
However, a large amount of flame retarder must be added to impart a high flame retarding effect to the resin, resulting in the problem of bleeding-out of the resin.
In addition, a resin composition comprising a bromine-containing flame retarder exhibits impaired processability. In particular, release of the flame retarder or its decomposition products produces an unpleasant odor, creates noxious compounds, and soils the forming molds.
The addition of an increased amount of flame retarder in order to achieve a high level of flame retardancy induces a problem of producing an increased amount of noxious materials, such as dioxane, furane, and the like during the molding process and during combustion.
As a solution to this type of problem, the addition to the resin material of a compound containing phosphorus and/or nitrogen as a flame retarder in place of the bromine compound has been proposed.
These compounds, however, entail a problem of releasing the flame retarder or its decomposition products and creating noxious compounds, although no particular adverse effect is imparted to the processability of the resin composition.
In addition, the flame retardancy effect from these compounds is extremely low as compared to that from the bromine-containing compounds.
Also, a flame-retardant resin composition to which these compounds have been added does not have adequate flame retardancy and may cause dripping during combustion. Dripping can be the cause of the spread of fire during a conflagration. Suppressing dripping is, therefore, important in the flame-retarding technology.
An object of the present invention is to provide a flame-retardant resin composition exhibiting reduced bleed-out of the flame retarder, by copolymerizing a halogen-substituted styrene in the resin, and, further, by incorporating a fluorine-containing resin, to provide the resin composition with a high level of flame retardancy and reduced dripping phenomenon during combustion, as well as superior resistance to impact and excellent moldability. The resin composition can produce formed products with a superior external appearance.